Grooved pulleys or sheaves have been produced for many years with grooves in the outer periphery thereof for mounting on rotating shafts for receiving belts in the grooves to transmit motion either to or from the shaft on which the pulley is mounted. These grooved pulleys have been produced by a variety of manufacturing procedures such as stamping, spinning or slitting of sheet steel or formed by metal casting or forging operations. Even though the particular manufacturing operation for producing such pulleys is carried out with precision and accuracy, an unbalance may result in the final produced pulley. Any unbalance in a rotating mass such as a pulley will result in noise and vibration which shortens the life of the pulley, shaft mounting bearings and attached belts in addition to producing an unsatisfactory condition to the vehicle or equipment on which the pulley is mounted. Thus, it is necessary that a pulley be balanced by some means to eliminate any unbalance in the pulley prior to mounting it on a shaft of a vehicle or other equipment on which it may be used.
Various methods and devices have been devised in the past for eliminating pulley unbalance such as by placing putty on the hub wall or annular side wall of the pulley as a counterbalancing weight at the location necessary to correct for the unbalance. Another manner of correcting such unbalance is to weld slugs of metal at the necessary position on the hub wall or annular side wall to correct for the unbalance. Also another means of balancing pulleys is to remove metal from the area where the unbalance occurs by drilling or milling procedures. Still other methods and devices involve the attachment of metal components on the pulley by rivets, bolts or splined connections with the hubs. Examples of such prior balancing means for a pulley or rotating object are shown in U.S. Pat. Nos. 79,405; 2,216,308; 2,494,756; 2,993,386; 3,349,640; 3,611,829; 3,808,660 and 4,003,265.
Although these existing balancing means may provide a satisfactory solution to an unbalanced condition of a rotating member, the mechanism by which the unbalanced condition is eliminated is relatively expensive to produce and install on the rotating member. For example, when a balancing device is mounted on a pulley that is used on a passenger automobile or vehicle, even a savings in material and installation cost of a few cents will result in a considerable cumulative savings to the manufacturer since millions of such vehicles are produced having the balanced pulley as a part thereof. One problem that has occured with some of the prior balancing devices is that the counterbalance weight such as putty or welded globs of metal would loosen and fall off the pulley due to the centrifugal forces exerted thereon. Still other devices had to be rebalanced when the pulley was removed from the shaft for repair or when performing work on the particular equipment on which the pulley was mounted. If the pulley was not reinstalled in the correct position, it would multiply the unbalanced condition. Often the mechanic performing the work would not be aware of the unbalanced condition of the pulley nor would he have available equipment for checking the balance thereof.
Thus, the need has existed for an extremely simple and inexpensive balancing device which can be permanently mounted on a pulley to balance the same which will not become loose or disengaged from the pulley after long periods of use or when subjected to centrifugal forces and used in harsh environments as can occur with prior balancing means and devices once attached to the pulley, and which will not require any further adjustment or balancing even if the pulley is removed from its shaft for maintenance purposes.